The need for eyeglasses has become an unfortunate reality for an increasing number of individuals. In the case of prescription eyeglasses, separate lenses are required to be inserted into and retained by an eyeglass frame. During the useful life of a single pair of eyeglass frames, it is likewise not uncommon to face a situation where an eyeglass wearer might require new or different lenses due to, for example, a change in prescription or damage to the lens. A not insignificant problem has arisen, since eyeglass frames need to allow for easy insertion and removal of lenses when a change is required, and also provide superior retention of lenses once properly positioned in the frame.
In plastic eyeglass frames, the lenses are often replaced and secured by softening the frame with heat and thereafter inserting the lenses into the softened frame. So called non-pliable eyeglass frames refer to frames that are made of materials other than plastic, such as metal and the like. In such non-pliable frames, a screw or threaded steel post is often used to tighten and secure the frame around the lenses. Lens replacement in non-pliable eyeglass frames has generally been accomplished by removal of the screw or threaded post which secures the top and bottom rim of the frames together. The screw is inserted through a bore in the top rim of a split rim eyeglass frame, and then connects to a receiving bore on the lower rim with the screw threads mating with the threads present inside the receiving bore in the lower rim.
This design has several disadvantages. During the useful life of the frames, the screw is repeatedly turned in the same direction to tighten the upper and lower rims around the lens. Over time the rims are subjected to vibration and other forces that tend to loosen the connection and cause the screw to back out of its tightened connection. In addition, repeated tightening of this connection often leads to damage to the frame as a result of bending or scratching caused by the tightening tool. Furthermore, the slot located on the head of the screw, the threads on the screw and inside the receiving lower rim are subject to wear and deformation from repeated tightening and loosening operations and the forces associated therewith. While the screw is the primary frame locking mechanism used in current industry practice, several alternative eyeglass frame locking mechanisms have been suggested.
For instance, in U.S. Pat. No. 5,270,743 to Hofmair et al, discloses a split rim eyeglass frame which includes two lens holding rings that share a common top rim. The bottom rim of the frame features integral coupling hooks and that engage cooperating recesses on the top rim of the frame to secure lenses therein. One primary disadvantage of this structure is that it requires the lens to be removed before the top and bottom rims can be disengaged. Repeated lens removals tend to weaken the frame and increase the risk of damage to lenses. In this device, the locking mechanism is not readily accessible, nor is it capable of being unlocked while the lens remains inside the frame.
U.S. Pat. No. 4,813,775 to Kaksonen, teaches a split rim eyeglass frame which includes an integral spring-mounted locking mechanism to allow the lens holders to expand for removal of the lens. The locking mechanism allows for repeated lens insertion and removal, but the frames must be manufactured specifically to accommodate it. In addition, it is foreseeable that the resilient clip used to lock the frame in place could rather easily be bent, twisted or otherwise deformed. Since only one spring mounted button on the frame needs to be depressed to unlock the frames, the possibility for undesired disengaging of the locking mechanism through inadvertent contact has no safeguard.
U.S. Pat. No. 2,080,853 to Nelson discloses an opthalmic mounting for attaching a nose pad to an eyeglass frame. A locking mechanism permits the nose pad to be movably mounted to the frame. The mounting includes two spaced fingers, each of which has a notch on its outer edge. The nose pad is mounted from the frame by pressing the two fingers together and inserting them into a receiving loop. Since the fingers of the locking mechanism are flat, they can easily be bent or otherwise damaged during insertions or removals. Further, in order to release the locking mechanism, it is necessary to squeeze the fingers of the mechanism together and push them through the receiving loop.
Thus, there is a need in the art for an eyeglass frame locking mechanism which is durable and can be repeatedly inserted and secured easily within a cooperating locking compartment and does not require the use of a threaded fastener. It is a purpose of this invention to fulfill this and other needs in the art which will become more apparent to the skilled artisan once given the following disclosure.